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Background: Hi-GAL image of l=299°

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Background: Hi-GAL image of l=299°

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  1. Filamentary Structures in Molecular Cloudsand their connection with Star FormationE.Schisano1, S.Molinari1, D.Polychroni1, D.Elia1, M.Pestalozzi1, R.Plume2and other members of Hi-GAL Team1 Istituto Fisica dello Spazio Interplanetario – Roma – INAF2 Department of Physics & Astronomy - University of Calgary - Canada Background: Hi-GAL image of l=299°

  2. What Herschel is saying us 2°x2° maps of the Galactic Plane observed in the Hi-GAL survey Filaments Everywhere! Cores Distribuited preferentially along filaments Second derivative filtering to enanche the structures contrast respect the diffuse emission SPIRE 250 μm detected cores Herschel observations confirmed the presence of filamentary structures with different scales and their association with cores/clumps. (Molinari et al. 2010, Andre et al. 2010).

  3. Filaments are an initial stage of the star formation that is not well studied. Large scale surveys allow a census of such structures to constrain their properties. Our goal is to use the potentiality of Hi-GAL survey to build up a catalog of filamentary structures on GP maps, for which we determine: Morphological Properties(length and width) linked to the filament formation process (sweeping/compression of matter, fragmentation etc). Physical Properties (mass, virial mass per unit length, temperature, column density) mechanisms active in such structures. Comparison with classical filament models (Ostriker et al. 1964, Fiege et al. 2000,2004) Correlation with the embedded cores (core shapes, core elongation, cores reciprocal distances – scales of filament fragmentation)

  4. MIPS 24 μm PACS 160 μm HII region (?) SPIRE 250 μm SPIRE 500 μm IRDC 10' • Filament definition – disentangling from diffuse ISM emission • Large amount of structures – Need of automatic algorithms Sample of Hi-GAL tile centered at l = 59°

  5. Filament identification Algorithm Image processing techniques to develop algorithms able to identify filamentary structures. Filament: Structure that is concave down along two different principal axes and is almost flat in the other one. (Aragon-Calvo et al.2007, Bond et al 2010) Elongated cylindrical-like patterns are traced by the lowest eigenvalue (λ1 << λ2) and the eigenvectors (A1,A2) of the Hessian matrix computed in each pixel. Extended not elongated regions are rejected by criteria on the highest eigenvalue and the eigenvectors Still in development – Work in progress! Technical Issues: Noise reduction filtering, better background estimation, sentivity to larger scales (> tens arcmin) structures (ok for Hi-GAL).

  6. Example of filament extraction SPIRE 250 PACS 160 SPIRE 500 Filament axis Filament Cores

  7. (very) Preliminary Results Sample of fitted SED Integrating the flux in the identified filament regions in various band we build the SED of such structures and by greybody fitting we determine the physical properties. Masses around few 10-100 Msun Temperature hotter than the typical IRDC (~12 K Peretto et al. 2009) Background determination is still not correct on Herschel maps with intense extended emission (masses underestimated). Lengths are of few arcminutes (~ tens pc) Widths are ~ 0.8-1.4’ ( ≤ 1 pc) <d> = 2.7 kpc – Russeil et al submitted We plan to use molecular line data to determine Δv and the virial masses. Currently we have data from 12CO and 13CO (J 1->0), but we are submitting proposals for higher transition lines to constrain gas physical properties. T = 19.2 K M = 361. Msun T = 17.5 K M = 125. Msun T = 18.6 K M = 22. Msun T = 18.5 K M = 19. Msun Supporting Magnetic Field Comparison with Classical models Fiege et al 2004 Binding Magnetic Field

  8. Summary (or... just the beginning) Herschel maps revealed maps reveal the rich and complex structure of star formation region with gas and dust arranged in filaments associated with embedded pre/proto- stellar cores. Filamentary structures, even if spread everywhere, are still not well studied, as well it has to be clarified their precise role in star formation. Simulations with different prescriptions are able to reproduce qualitatively the observed filamentary patterns, but no systematic study exist yet in literature. We developed an algorithm to identify cylindrical-like structures on Herschel maps to overcome the difficulties in the definition filaments in an objective way. We will apply the algorithm to the maps of Galactic plane to build a robust catalog of filaments, for which we will determine morphological and physical properties to be compared with the classical models for such structures.

  9. MIPS 24 μm PACS 70 μm PACS 160 μm SPIRE 250 μm SPIRE 350 μm SPIRE 500 μm

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